1. Technical Field
Improved dual rocking piston pumps are disclosed that employ a cantilevered rotor and stator supported by a single bracket without the need for a rear bell housing thereby providing a compact design. The disclosed pumps may be made with fewer parts than conventional dual rocking piston pumps, therefore resulting in lower manufacturing costs and reduced weight in a compact design.
2. Description of the Related Art
Dual rocking piston compressors, diaphragm compressors and vacuum pumps all use the reciprocating motion of a piston to produce increased pressures within a control volume, such as a cylinder. The length of the stroke of the piston determines the compression ratio for the fixed control volume. Dual rocking piston pumps are often used for medical applications, such as used in oxygen concentrators, because they are compact.
One problem with conventional dual rocking piston pumps is that they can create noise and vibration as the pistons reciprocally stroke, especially if the two pistons are designed for different outputs, thereby leading to balancing problems. If each piston assembly produces a different output, different rod top/retainer/diaphragm diameters, forces of different magnitudes are imposed on the drive shaft by each piston assembly. Shaking or vibrations arise as the drive shaft rotates because of the imbalance in the forces imposed by each piston assembly. Further, it is often desirable to design dual rocking piston pumps with unequal piston strokes. A dual opposed rocking piston pump with unequal strokes is also inherently out of balance. Because the strokes are different, the opposed reciprocating piston assemblies are traveling different distances during each revolution. As a result, the acceleration of one piston assembly is not equal to the acceleration of the other piston assembly. The diameters of the retainers, rod tops or diaphragms may or may not be equal and the mass of the opposed reciprocating components may or may not be equal. As a result, the forces created by the opposed reciprocating components may not be equal resulting in unwanted shaking, vibration or noise. Co-pending U.S. application Ser. No. 11/776,310 addresses this problem, and is incorporated herein by reference.
However, it would be desirable to reduce the size, weight and number of required parts for dual rocking piston pumps. Obviously, pumps used in medical applications and other applications where the pump is moved need to be lightweight, as well as reliable. Similarly, the pumps should have a compact design which renders them easy to incorporate into existing equipment and environments. Any design changes, of course, must not result in compromising the recent improvements in terms of noise and vibration.
Accordingly, there remains a need for an improved rocking piston pump or compressor with excellent balance and quiet operation that, is also lightweight, compact and requires fewer parts, without making the pump noisy or compromising the reliability or efficiency of the pump.